Traditional strapdown inertial navigation algorithm based on geography coordinate system can not directly obtain the navigation parameters under launch inertial coordinate system. It’s difficult for high orbiters such as aerospace vehicles to be provided with high precision, high reliability navigation system. Therefore, this paper carried out a research on the strapdown inertial navigation algorithm under launch inertial coordinate system and established SINS/GPS inertial navigation model on the basis of extended Kalman filter. The navigation measurement information obtained by the sensors under launch inertial coordinate system was directly used to calculate position and attitude of the aircraft. To verify the validity of the integrated navigation algorithm, the hardware platform based on XSENS inertial device, GPS receiver and STM32 embedded system was established. Experimental results indicated that the SINS/GPS integrated navigation system under launch inertial coordinate system can achieve higher navigation precision. Thus algorithm proposed in this paper is valid and reasonable.